Recently, development is progressing in methods for executing image processing on images captured by cameras and the like, automatically detecting the occurrence of situations that differ from normal in the captured image, and determining whether or not a specific subject is included in the captured image. Such image determinations generally employ a method of comparing a feature amount in a captured image and in an image of the subject serving as a reference for determination (determination-use image).
However, for example, for captured images such as those captured outside, the image capture conditions of the captured image sometimes differ from the image capture conditions of the determination-use image, such as by changes in the brightness of light illuminating the subject to be determined. The detection precision and the precision of determination of the subject are therefore lowered in abnormal situations.
Hitherto, reference data for feature amounts of the captured images have therefore first been obtained from a relationship between predetermined brightness data and a feature amount of the captured image, based on brightness data of the captured images. A monitoring device has been proposed that then automatically detects the occurrence of situations that differ from normal captured images, even if the captured image is captured in conditions of changed illumination, by comparing the difference between obtained reference data and the feature amount obtained from the captured image.